Electron transport and shot noise in double-barrier resonant diodes: The role of Pauli and Coulomb correlations

We present a theoretical study of electron transport and shot noise in double barrier resonant diodes within the sequential tunneling model. We investigate the role played by Pauli principle and Coulomb interaction on the current voltage (I-V) characteristics and the Fano factor by varying carrier concentration and lattice temperature. At 4.2K we obtain the bistable I-V characteristics of Z type. In the region of low and intermediate voltages for a sufficiently low electron concentration in the contacts the Fano factor exhibits two successive suppressed regimes associated with Pauli blockade and Coulomb correlation, respectively. By further increasing the voltage shot noise enhancement is found to be a precursor indicator that the device is approaching an instability regime in analogy with the case of phase transitions. In the bistable region hysteresis effects on different transport and parameters are analyzed. At 77K and increasing temperatures for a carrier concentration of 5×10¹⁶cm^-3 the diode exhibits the usual negative differential conductance (NDC) characteristic. For voltages below NDC only Coulomb correlation remains effective, leading to a suppressed Fano factor intermediate between $0.5--1.$ For voltages just above NDC a moderate enhancement of the Fano factor up to values around 8 is evidenced. Theoretical findings provide a detailed physical interpretation of experimental results available in the literature and predict features to be confirmed by further experiments.